Technical Abstract:
Particulate organic matter (POM) is a transitory pool of soil organic matter having a decomposition rate intermediate between fresh plant litter and humified stable organic matter. Because POM is sensitive to changes in land use and soil management, it has been widely adopted as an indicator of soil quality in agricultural ecosystems. However, determination of POM mass is difficult in semi-arid sandy soils because the weight of POM material is very small relative to the weight of sand. We tested loss-on-ignition (LOI) as a method to quantify the mass of POM associated with the (POM+sand) fraction of semi-arid sandy soils, and compared direct analysis of POM-C with POM-C calculated by the difference between whole soil C and mineral-associated C. Preliminary results indicate that POM-C by direct analysis was highly correlated with POM-C by calculation (r2 = 0.91), with POM-C by calculation averaging 14.1% higher than POM-C by direct analysis. The precision of determining POM mass by LOI will be discussed.